Processes and compositions for organic rankine cycles for generating mechanical energy from heat

ABSTRACT

Disclosed are compositions of novel working fluids uniquely designed for higher cycle efficiencies leading to higher overall system efficiencies. In particular, these working fluids are useful in Organic Rankine Cycle systems for efficiently converting heat from any heat source into mechanical energy. The present invention also relates to novel processes for recovering heat from a heat source using ORC systems with a novel working fluid comprising at least about 20 weight percent cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), or mixtures thereof.

BACKGROUND

1. Field of the Disclosure

The present invention generally relates to novel working fluids uniquelydesigned for reduced impact on climate change and higher cycleefficiencies, thereby leading to higher overall system efficiencies. Inparticular, these working fluids are useful in Organic Rankine Cycle(ORC) systems for efficiently converting heat from various heat sourcesinto mechanical energy. The present invention also relates to novelprocesses for recovering heat from a heat source using ORC systems witha novel working fluid comprising at least about 20 weight percentcis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z),trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), or mixturesthereof.

2. Description of Related Art

Previous Rankine Cycle systems have used various working fluidsincluding flammable or combustible working fluids—fluids with relativelyhigh toxicity, fluids with relatively high global warming potentials(GWPs) and fluids with non-zero ozone depletion potentials (ODPs).Industry has been working on replacing ozone-depletingchlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).Non-flammable, low toxicity, environmentally sustainable working fluidsare highly desirable for Rankine Cycle applications.

It has been found that surprisingly, the novel working fluids of thepresent invention uniquely provide higher cycle efficiencies in ORCsystems that in turn result in higher overall system efficiencies in thepower cycle while offering low toxicity, no flammability, zero ODP, andvery low GWP.

SUMMARY OF THE INVENTION

In one embodiment, this invention relates to a process for recoveringheat from a heat source and generating mechanical energy, comprising thesteps of:

-   (a) passing a first working fluid in liquid phase through a heat    exchanger or an evaporator, wherein said heat exchanger or said    evaporator is in communication with said heat source that supplies    said heat;-   (b) removing at least a portion of said first working fluid in a    vapor phase from said heat exchanger or said evaporator;-   (c) passing said at least a portion of said first working fluid in    vapor phase to an expander, wherein at least portion of said heat is    converted into mechanical energy;-   (d) passing said at least a portion of said first working fluid in    vapor phase from said expander to a condenser, wherein said at least    a portion of said first working fluid in vapor phase is condensed to    a second working fluid in liquid phase;-   (e) optionally, compressing and mixing said second working fluid in    liquid phase with said first working fluid in liquid phase in Step    (a); and-   (f) optionally, repeating Steps (a) through (e), at least one time;    wherein at least about 20 weight percent of said first working fluid    comprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.

This invention further relates to a process for recovering heat from aheat source and generating mechanical energy, comprising the steps of:

-   (a) compressing a first working fluid in liquid phase above said    first working fluid's critical pressure;-   (b) passing said first working fluid from Step (a) through a heat    exchanger or a fluid heater and heating said first working fluid to    a temperature that is higher or lower than the critical temperature    of said first working fluid, wherein said heat exchanger or said    fluid heater is in communication with said heat source that supplies    said heat;-   (c) removing at least a portion of the heated said first working    fluid from said heat exchanger fluid heater;-   (d) passing said at least a portion of the heated said first working    fluid to an expander,    wherein at least portion of said heat is converted into mechanical    energy, and    wherein the pressure on said first at least a portion of the heated    said first working fluid is reduced to below the critical pressure    of said first working fluid, thereby rendering said at least a    portion of the heated said first working fluid to a first working    fluid vapor or a first working fluid mixture of vapor and liquid;-   (e) passing said first working fluid vapor or said first working    fluid mixture of vapor and liquid from said expander to a condenser,    wherein said at least a portion of said working fluid vapor or said    working fluid mixture of vapor and liquid is fully condensed to a    second working fluid in liquid phase;-   (f) optionally, compressing and mixing said second working fluid in    liquid phase with said first working fluid in liquid phase in Step    (a);-   (g) optionally, repeating Steps (a) through (f), at least one time;    wherein at least about 20 weight percent of said first working fluid    comprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.

In one embodiment, this invention further relates to a compositioncomprising HFO-1336mzz-Z at a temperature in the range of from about250° C. to about 300° C., wherein said HFO-1336mzz-Z content is in therange of from about 50 weight percent to about 99.5 weight percent.

In yet another embodiment, this invention relates to an Organic RankineCycle System extracting heat at an operating pressure in the range fromabout 3 MPa to about 10 MPa, wherein about 20 weight percent of saidworking fluid comprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixturesthereof.

In another embodiment, this invention relates to a composition asworking fluid for power cycles, wherein the temperature of saidcomposition is in the range of from about 50° C. to about 400° C., andwherein about 20 weight percent of said composition comprisesHFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.

In another embodiment, this invention relates to a method for replacingHFC-245fa in a power cycle system. The method comprises removing saidHFC-245fa from said power cycle system and charging said system with aworking fluid comprising HFO-1336mzz-Z, HFO-1336mzz-E, or mixturesthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a heat source and an organic Rankine cyclesystem in direct heat exchange according to the present invention.

FIG. 2 is a block diagram of a heat source and an organic Rankine cyclesystem which uses a secondary loop configuration to provide heat from aheat source to a heat exchanger for conversion to mechanical energyaccording to the present invention.

FIG. 3 shows the energy efficiency of transcritical Organic RankineCycles operating with HFO-1336mzz-Z as the working fluid as a functionof the pressure of the fluid heater for selected temperatures of theworking fluid at the expander inlet (T_(cond)=54.44° C.;T_(subcooling)=7.78° C.; Expander Efficiency=0.85; and PumpEfficiency=0.85).

FIG. 4 shows the energy efficiency of transcritical Organic RankineCycles operating with HFO-1336mzz-Z as the working fluid as a functionof the pressure of the fluid heater for selected temperatures of theworking fluid at the expander inlet (T_(cond)=40° C.; T_(subcooling)=0°C.; Expander Efficiency=0.85; and Pump Efficiency=0.85).

FIG. 5 shows a transcritical ORC with a completely dry expansion.

FIG. 6 shows a transcritical ORC with partial condensation duringexpansion but dry vapor at the expander exit.

FIG. 7 shows a transcritical ORC with wet expansion and with thetemperature at the expander inlet higher than the critical temperatureof the working fluid.

FIG. 8 shows a transcritical ORC with wet expansion, but with thetemperature at the expander inlet lower than the critical temperature ofthe working fluid.

DETAILED DESCRIPTION

Global warming potential (GWP) is an index for estimating relativeglobal warming contribution due to atmospheric emission of a kilogram ofa particular greenhouse gas compared to emission of a kilogram of carbondioxide. GWP can be calculated for different time horizons showing theeffect of atmospheric lifetime for a given gas. The GWP for the 100 yeartime horizon is commonly the value referenced.

Net cycle power output is the rate of mechanical work generation at theexpander (e.g., a turbine) less the rate of mechanical work consumed bythe compressor (e.g., a liquid pump).

Volumetric capacity for power generation is the net cycle power outputper unit volume of working fluid (as measured at the conditions at theexpander outlet) circulated through the cycle.

Cycle efficiency (also referred to as thermal efficiency) is the netcycle power output divided by the rate at which heat is received by theworking fluid during the heating stage.

Subcooling is the reduction of the temperature of a liquid below thatliquid's saturation point for a given pressure. The saturation point isthe temperature at which a vapor composition is completely condensed toa liquid (also referred to as the bubble point). But subcoolingcontinues to cool the liquid to a lower temperature liquid at the givenpressure. Subcool amount is the amount of cooling below the saturationtemperature (in degrees) or how far below its saturation temperature aliquid composition is cooled.

Superheat is a term that defines how far above its saturationtemperature (the temperature at which, if the composition is cooled, thefirst drop of liquid is formed, also referred to as the “dew point”) avapor composition is heated.

Temperature glide (sometimes referred to simply as “glide”) is theabsolute value of the difference between the starting and endingtemperatures of a phase-change process by a refrigerant within acomponent of a refrigerant system, exclusive of any subcooling orsuperheating. This term may be used to describe condensation orevaporation of a near azeotrope or non-azeotropic composition. Averageglide refers to the average of the glide in the evaporator and the glidein the condenser of a specific chiller system operating under a givenset of conditions.

The term “dry” as used in relation to “a dry expansion”, for instance,is meant to mean an expansion that takes place entirely in the vaporphase with no liquid working fluid present. Thus, “dry” as used hereindoes not relate to the presence or absence of water.

An azeotropic composition is a mixture of two or more differentcomponents which, when in liquid form under a given pressure, will boilat a substantially constant temperature, which temperature may be higheror lower than the boiling temperatures of the individual components, andwhich will provide a vapor composition essentially identical to theoverall liquid composition undergoing boiling. (see, e.g., M. F. Dohertyand M. F. Malone, Conceptual Design of Distillation Systems, McGraw-Hill(New York), 2001, 185-186, 351-359).

Accordingly, the essential features of an azeotropic composition arethat at a given pressure, the boiling point of the liquid composition isfixed and that the composition of the vapor above the boilingcomposition is essentially that of the overall boiling liquidcomposition (i.e., no fractionation of the components of the liquidcomposition takes place). It is also recognized in the art that both theboiling point and the weight percentages of each component of theazeotropic composition may change when the azeotropic composition issubjected to boiling at different pressures. Thus, an azeotropiccomposition may be defined in terms of the unique relationship thatexists among the components or in terms of the compositional ranges ofthe components or in terms of exact weight percentages of each componentof the composition characterized by a fixed boiling point at a specifiedpressure.

For the purpose of this invention, an azeotrope-like composition means acomposition that behaves substantially like an azeotropic composition(i.e., has constant boiling characteristics or a tendency not tofractionate upon boiling or evaporation). Hence, during boiling orevaporation, the vapor and liquid compositions, if they change at all,change only to a minimal or negligible extent. This is to be contrastedwith non-azeotrope-like compositions in which during boiling orevaporation, the vapor and liquid compositions change to a substantialdegree.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a composition,process, method, article, or apparatus that comprises a list of elementsis not necessarily limited to only those elements but may include otherelements not expressly listed or inherent to such composition, process,method, article, or apparatus. Further, unless expressly stated to thecontrary, “or” refers to an inclusive or and not to an exclusive or. Forexample, a condition A or B is satisfied by any one of the following: Ais true (or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

The transitional phrase “consisting of” excludes any element, step, oringredient not specified. If in the claim such would close the claim tothe inclusion of materials other than those recited except forimpurities ordinarily associated therewith. When the phrase “consistsof” appears in a clause of the body of a claim, rather than immediatelyfollowing the preamble, it limits only the element set forth in thatclause; other elements are not excluded from the claim as a whole.

The transitional phrase “consisting essentially of” is used to define acomposition, method or apparatus that includes materials, steps,features, components, or elements, in addition to those literallydisclosed provided that these additional included materials, steps,features, components, or elements do materially affect the basic andnovel characteristic(s) of the claimed invention. The term ‘consistingessentially of’ occupies a middle ground between “comprising” and‘consisting of’.

Where applicants have defined an invention or a portion thereof with anopen-ended term such as “comprising,” it should be readily understoodthat (unless otherwise stated) the description should be interpreted toalso describe such an invention using the terms “consisting essentiallyof” or “consisting of.”

Also, use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present invention, suitablemethods and materials are described below. All publications, patentapplications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

E-1,1,1,1,4,4,4-hexafluoro-2-butene (also known as HFO-1336mzz-E ortrans-HFO-1336mzz and having the structure E-CF₃CH═CHCF₃) andZ-1,1,1,4,4,4-hexafluoro-2-butene (also known as HFO-1336mzz-Z orcis-HFO-1336mzz and having the structure Z—CF₃CH═CHCF₃), may be made bymethods known in the art, such as by hydrodechlorination of2,3-dichloro-1,1,1,4,4,4-hexafluoro-2-butene, as described in U.S.Patent Application Publication No. US 2009/0012335 A1, incorporatedherein by reference.

Processes for Recovering Heat or Converting Heat into Mechanical Energy

For the purposes of the present invention, transcritical Organic RankineCycle is defined as an Organic Rankine Cycle which extracts heat at apressure higher than the critical pressure of the working fluid used inthe cycle.

In one embodiment, the present invention relates to novel processes forrecovering heat from a heat source and generating mechanical energyusing Organic Rankine Cycle (“ORC”) systems which employ a novel workingfluid.

In one embodiment, the above process for recovering heat from a heatsource and generating mechanical energy, comprises the following steps:

-   (a) passing a first working fluid in liquid phase through a heat    exchanger or an evaporator, wherein said heat exchanger or said    evaporator is in communication with said heat source that supplies    said heat;-   (b) removing at least a portion of said first working fluid in a    vapor phase from said heat exchanger or said evaporator;-   (c) passing said at least a portion of said first working fluid in    vapor phase to an expander, wherein at least portion of said heat is    converted into mechanical energy;-   (d) passing said at least a portion of said first working fluid in    vapor phase from said expander to a condenser, wherein said at least    a portion of said first working fluid in vapor phase is condensed to    a second working fluid in liquid phase;-   (e) optionally, compressing and mixing said second working fluid in    liquid phase with said first working fluid in liquid phase in Step    (a); and-   (f) optionally, repeating Steps (a) through (e), at least one time;    wherein at least about 20 weight percent of said first working fluid    comprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In    another embodiment, the first working fluid comprises at least 30    weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In    another embodiment, the first working fluid comprises at least 40    weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In    another embodiment, the first working fluid comprises at least 50    weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.

The working fluid described above comprises at least about 20 weightpercent cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or at least about 20 weight percent of a mixturethereof. In another embodiment, the working fluid comprises at least 30weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. Inanother embodiment, the working fluid comprises at least 40 weightpercent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In anotherembodiment, the working fluid comprises at least 50 weight percentHFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In a suitableembodiment, said at least about 20 weight percentcis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or said at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or said at least about 20 weight percent of a mixturethereof is selected from the following percentage content of the workingfluid:

-   -   about 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,        34, 35, 36, 37, 38, 39, 40, 41,42, 43, 44, 45, 46, 47, 48, 49,        50, 50.5, 51, 52, 52.5, 53, 53.5, 54, 54.5, 55, 55.5, 56, 56.5,        57, 57.5, 58, 58.5, 59, 59.5, 60, 60.5, 61, 61.5, 62, 62.5, 63,        63.5, 64, 64.5, 65, 65.5, 66, 66.5, 67, 67.5, 68, 68.5, 69,        69.5, 70, 70.5, 71, 71.5, 72, 72.5, 73, 73.5, 74, 74.5, 75,        55.5, 76, 76.5, 77, 77.5, 78, 78.5, 79, 79.5, 80, 80.5, 81,        81.5, 82, 82.5, 83, 83.5, 84, 84.5, 85, 85.5, 86, 86.5, 87,        87.5, 88, 88.5, 89, 89.5, 90, 90.5, 91, 91.5, 92, 92.5, 93,        93.5, 94, 94.5, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5, 99,        99.5, and about 100%.

In another suitable embodiment, said at least about 20 weight percentcis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or said at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or said at least about 20 weight percent of a mixturethereof is selected from a range defined by any two percentage numbersabove (inclusive of endpoints).

In one embodiment of the above process, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 10 weight percent HFO-1336mzz-E and 90 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises at least about 15 weight percentHFO-1336mzz-E and 85 or more weight percent HFO-1336mzz-Z. In anotherembodiment, wherein the working fluid comprises a mixture ofHFO-1336mzz-Z and HFO-1336mzz-E, the working fluid comprises at leastabout 20 weight percent HFO-1336mzz-E and 80 or more weight percentHFO-1336mzz-Z. In another embodiment, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 25 weight percent HFO-1336mzz-E and 75 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises from about 25 weight percent to about 75weight percent HFO-1336mzz-E and from about 75 weight percent to about25 weight percent HFO-1336mzz-Z.

The working fluid can also comprise less than about 80 weight percent ofone or more of other components selected from the following:

-   -   cis-HFO-1234ze; trans-HFO-1234ze; HFO-1234yf; HFO-1234ye-E or Z;        HFO 1225ye(Z); HFO-1225ye(E); HFO-1225yc; HFO-1243zf        (3,3,3-trifluoropropene); HFO-1233zd-E or Z; HFO-1233xf;        CF₃CH═CHCF₃11 (E); (CF₃)₂CFCH═CHF (E & Z); (CF₃)₂CFCH═CF₂;        CF₃CHFC═CHF (E & Z); (C₂F5)(CF₃)C═CH₂; HFC-245fa; HFC-245eb;        HFC-245ca; HFC-245cb; HFC-227ea; HFC-236cb; HFC-236ea;        HFC-236fa; HFC-365mfc; HFC-43-10mee; CHF₂—O—CHF₂; CHF₂—O—CH₂F;        CH₂F—O—CH₂F; CH₂F—O—CH₃; cyclo-CF₂—CH₂—CF₂—O;        cyclo-CF₂—CF₂—CH₂—O; CHF₂—O—CF₂—CHF₂; CF₃—CF₂—O—CH₂F;        CHF₂—O—CHF—CF₃; CHF₂—O—CF₂—CHF₂; CH₂F—O—CF₂—CHF₂; CF₃—O—CF₂—CH₃;        CHF₂—CHF—O—CHF₂; CF₃—O—CHF—CH₂F; CF₃—CHF—O—CH₂F; CF₃—O—CH₂—CHF₂;        CHF₂—O—CH₂—CF₃; CH₂F—CF₂—O—CH₂F; CHF₂—O—CF₂—CH₃; CHF₂—CF₂—O—CH₃;        CH₂F—O—CHF—CH₂F; CHF₂—CHF—O—CH₂F; CF₃—O—CHF—CH₃; CF₃—CHF—O—CH₃;        CHF₂—O—CH₂—CHF₂; CF₃—O—CH₂—CH₂F; CF₃—CH₂—O—CH₂F;        CF₂H—CF—CF₂—O—CH₃; propane; cyclopropane; butane; isobutane;        n-pentane; isopentane; neopentane; cyclopentane; n-hexane;        isohexane; heptane; trans-1,2-dichloroethylene, and mixtures        with cis-HFO-1234ze and HFC-245fa.

In one embodiment, the working fluid comprises 80 weight percent or lessof at least one of the above compounds. In another embodiment, theworking fluid comprises 70 weight percent or less of at least one of theabove compounds. In another embodiment, the working fluid comprises 60weight percent or less of at least one of the above compounds. Inanother embodiment, the working fluid comprises 50 weight percent orless of at least one of the above compounds.

In one embodiment, the working fluid for extracting heat may consist ofHFO-1336mzz-Z. In another embodiment, the working fluid for extractingheat may consist of HFO-1336mzz-E. In another embodiment, the workingfluid for extracting heat may consist of a mixture of HFO-1336mzz-Z andHFO-1336mzz-E.

Note that while the working fluid in the process description above isidentified as a “first” working fluid and as a “second” working fluid,it should be understood that the difference between the two workingfluids is only that the first working fluid is the fluid that enters theORC system while the second working fluid is the fluid that enters theORC system after it has undergone at least one step of the processoutlined in above.

In one embodiment of the above process, the efficiency of convertingheat to mechanical energy (cycle efficiency) is at least about 7%. In asuitable embodiment, the efficiency can be selected from the following:

-   -   about 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13,        13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19,        19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, and        about 25%.

In another embodiment, the efficiency is selected from a range that hasendpoints (inclusive) as any two efficiency numbers supra. It is to beunderstood that the instantaneous efficiency of the ORC system may varyat any given time depending upon the several variables in the ORC systemsuch as the source temperature and the pressure of the working fluid andits temperature.

In one embodiment of the above process, the working fluid isHFO-1336mzz-Z with minimum amounts of other components, and theevaporator operating temperature (highest temperature at which heat isextracted by the working fluid) is less than or equal to about 171° C.In a suitable embodiment, the temperature of operation can be any one ofthe following temperatures or within the range (inclusive) defined byany two numbers below:

-   -   about 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,        74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89,        90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,        105, 106, 107, 108, 109,        110,111,112,113,114,115,116,117,118,119,120,121,122,123, 124,        125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,        138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150,        151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, and        about 163, 164, 165, 166, 167, 168, 169, 170, and about 171° C.

In another embodiment of the above process, the working fluid isprimarily HFO-1336mzz-E, and the evaporator operating temperature(highest temperature at which heat is extracted by the working fluid) isless than or equal to about 137° C. In a suitable embodiment, thetemperature of operation can be any one of the following temperatures orwithin the range (inclusive) defined by any two numbers below:

-   -   about 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,        74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89,        90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,        105, 106, 107, 108, 109,        110,111,112,113,114,115,116,117,118,119, 120, 121,122, 123, 124,        125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, and        about 137° C.

In another embodiment, the working fluid is a mixture of HFO-1336mzz-Zand HFO-1336mzz-E and the evaporator operating temperature (highesttemperature at which heat is extracted by the working fluid) is in therange from about 137° C. to about 171° C.

In one embodiment of the above process, the evaporator operatingpressure is less than about 2.5 MPa. In a suitable embodiment, thepressure of operation can be any one of the following pressures orwithin the range (inclusive) defined by any two numbers below:

-   -   about 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40,        1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90,        1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40,        2.45, and about 2.50 MPa.

In one embodiment of the above process, said working fluid has a GWP ofless than 35. In a suitable embodiment, the GWP can be any one of thefollowing numbers or within the range (inclusive) defined by any twonumbers below:

-   -   5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12,        12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18,        18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24,        24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30,        30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, and about 35.

FIG. 1 shows a schematic of one embodiment of the ORC system for usingheat from a heat source. A heat supply heat exchanger 40 transfers heatsupplied from a heat source 46 to the working fluid entering the heatsupply heat exchanger 40 in liquid phase. The heat supply heat exchanger40 is in thermal communication with the source of heat (thecommunication may be by direct contact or another means). In otherwords, the heat supply heat exchanger 40 receives heat energy from theheat source 46 by any known means of thermal transfer. The ORC systemworking fluid circulates through the heat supply heat exchanger 40 whereit gains heat. At least a portion of the liquid working fluid convertsto vapor in the heat supply heat exchanger (an evaporator, in somecases) 40.

The working fluid now in vapor form is routed to the expander 32 wherethe expansion process results in conversion of at least a portion of theheat energy supplied from the heat source into mechanical energy,usually shaft energy. Shaft power can be used to do any mechanical workby employing conventional arrangements of belts, pulleys, gears,transmissions or similar devices depending on the desired speed andtorque required. In one embodiment, the shaft can also be connected toan electric power-generating device 30 such as an induction generator.The electricity produced can be used locally or delivered to a grid.

The working fluid still in vapor form that exits the expander 32continues to the condenser 34 where adequate heat rejection causes thefluid to condense to liquid.

It is also desirable to have a liquid surge tank 36 located between thecondenser 34 and pump 38 to ensure there is always an adequate supply ofworking fluid in liquid form to the pump suction. The working fluid inliquid form flows to a pump 38 that elevates the pressure of the fluidso that it can be introduced back into the heat supply heat exchanger 40thus completing the Rankine cycle loop.

In an alternative embodiment, a secondary heat exchange loop operatingbetween the heat source and the ORC system can also be used. In FIG. 2,an organic Rankine cycle system is shown using a secondary heat exchangeloop. The main organic Rankine cycle operates as described above forFIG. 1. The secondary heat exchange loop shown in FIG. 2 operates asfollows: the heat from the heat source 46′ is transported to the heatsupply heat exchanger 40′ using a heat transfer medium (i.e., secondaryheat exchange loop fluid). The heat transfer medium moves from the heatsupply heat exchanger 40′ to a pump 42′ that pumps the heat transfermedium back to the heat source 46′. This arrangement offers anothermeans of removing heat from the heat source and delivering it to the ORCsystem. This arrangement provides flexibility by facilitating the use ofvarious fluids for sensible heat transfer. In fact, the working fluidsof this invention can be used as secondary heat exchange loop fluidsprovided the pressure in the loop is maintained at or above the fluidsaturation pressure at the temperature of the fluid in the loop.Alternatively, the working fluids of this invention can be used assecondary heat exchange loop fluids or heat carrier fluids to extractheat from heat sources in a mode of operation in which the workingfluids are allowed to evaporate during the heat exchange process therebygenerating large fluid density differences sufficient to sustain fluidflow (thermosyphon effect). Additionally, high-boiling point fluids suchas glycols, brines, silicones, or other essentially non-volatile fluidsmay be used for sensible heat transfer in the secondary loop arrangementdescribed. High-boiling point fluids may be those fluids with boilingpoints of 150° C. or higher. A secondary heat exchange loop can makeservicing of either the heat source or the ORC system easier since thetwo systems can be more easily isolated or separated. This approach cansimplify the heat exchanger design as compared to the case of having aheat exchanger with a high mass flow/low heat flux portion followed by ahigh heat flux/low mass flow portion.

Organic compounds often have an upper temperature limit above whichthermal decomposition will occur. The onset of thermal decompositionrelates to the particular structure of the chemical and thus varies fordifferent compounds. In order to access a high-temperature source usingdirect heat exchange with the working fluid, design considerations forheat flux and mass flow, as mentioned above, can be employed tofacilitate heat exchange while maintaining the working fluid below itsthermal decomposition onset temperature. Direct heat exchange in such asituation typically requires additional engineering and mechanicalfeatures which drive up cost. In such situations, a secondary loopdesign may facilitate access to the high-temperature heat source bymanaging temperatures while circumventing the concerns enumerated forthe direct heat exchange case.

Other ORC system components for the secondary heat exchange loopembodiment are essentially the same as described for FIG. 1. As shown inFIG. 2, a liquid pump 42′ circulates the secondary fluid (e.g., heattransfer medium) through the secondary loop so that it enters theportion of the loop in the heat source 46′ where it gains heat. Thefluid then passes to the heat exchanger 40′ where the secondary fluidgives up heat to the ORC working fluid.

In yet another embodiment, the present invention relates to the novelworking fluid uniquely designed for higher cycle efficiencies in powercycles, thereby leading to higher overall system efficiencies. Inparticular, these working fluids are useful in Organic Rankine Cycle(“ORC”) systems for efficiently converting heat from various heatsources into mechanical energy. This working fluid is described above.

Transcritical organic Rankine cycles

In one embodiment, organic Rankine cycles are transcritical cycles.Therefore, the present invention relates to a process for recoveringheat from a heat source, comprising the following steps:

-   (a) compressing a first working fluid in liquid phase above said    first working fluid's critical pressure;-   (b) passing said first working fluid from Step (a) through a heat    exchanger or a fluid heater and heating said first working fluid to    a temperature that is higher or lower than the critical temperature    of said first working fluid, wherein said heat exchanger or said    fluid heater is in communication with said heat source that supplies    said heat;-   (c) removing at least a portion of the heated said first working    fluid from said heat exchanger or fluid heater;-   (d) passing said at least a portion of the heated said first working    fluid to an expander,    wherein at least portion of said heat is converted into mechanical    energy, and    wherein the pressure on said at least a portion of the heated said    first working fluid is reduced to below the critical pressure of    said first working fluid, thereby rendering said at least a portion    of the heated said first working fluid to a first working fluid    vapor or a first working fluid mixture of vapor and liquid;-   (e) passing said first working fluid vapor or said first working    fluid mixture of vapor and liquid from said expander to a condenser,    wherein said at least a portion of said working fluid vapor or said    working fluid mixture of vapor and liquid is fully condensed to a    second working fluid in liquid phase;-   (f) optionally, compressing and mixing said second working fluid in    liquid phase with said first working fluid in liquid phase in Step    (a);-   (g) optionally, repeating Steps (a) through (f), at least one time;    wherein at least about 20 weight percent of said first working fluid    comprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In    another embodiment, the first working fluid comprises at least 30    weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In    another embodiment, the first working fluid comprises at least 40    weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In    another embodiment, the first working fluid comprises at least 50    weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.

In one embodiment of the above process, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 10 weight percent HFO-1336mzz-E and 90 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises at least about 15 weight percentHFO-1336mzz-E and 85 or more weight percent HFO-1336mzz-Z. In anotherembodiment, wherein the working fluid comprises a mixture ofHFO-1336mzz-Z and HFO-1336mzz-E, the working fluid comprises at leastabout 20 weight percent HFO-1336mzz-E and 80 or more weight percentHFO-1336mzz-Z. In another embodiment, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 25 weight percent HFO-1336mzz-E and 75 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises from about 25 weight percent to about 75weight percent HFO-1336mzz-E and from about 75 weight percent to about25 weight percent HFO-1336mzz-Z.

In one embodiment of the above process, the efficiency of convertingheat to mechanical energy (cycle efficiency) is at least about 7%. In asuitable embodiment, the efficiency can be selected from the following:

-   -   about 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13,        13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19,        19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, and        about 25%.

In another embodiment, the efficiency is selected from a range that hasendpoints (inclusive) as any two efficiency numbers supra.

The working fluid described above comprises at least about 20 weightpercent cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or at least about 20 weight percent of a mixturethereof. In a suitable embodiment, said at least about 20 weight percentcis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or said at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or said at least about 20 weight percent of a mixturethereof is selected from the following percentage content of the workingfluid:

-   -   about 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,        34, 35, 36, 37, 38, 39, 40, 41,42, 43, 44, 45, 46, 47, 48, 49,        50, 50.5, 51, 52, 52.5, 53, 53.5, 54, 54.5, 55, 55.5, 56, 56.5,        57, 57.5, 58, 58.5, 59, 59.5, 60, 60.5, 61, 61.5, 62, 62.5, 63,        63.5, 64, 64.5, 65, 65.5, 66, 66.5, 67, 67.5, 68, 68.5, 69,        69.5, 70, 70.5, 71, 71.5, 72, 72.5, 73, 73.5, 74, 74.5, 75,        55.5, 76, 76.5, 77, 77.5, 78, 78.5, 79, 79.5, 80, 80.5, 81,        81.5, 82, 82.5, 83, 83.5, 84, 84.5, 85, 85.5, 86, 86.5, 87,        87.5, 88, 88.5, 89, 89.5, 90, 90.5, 91, 91.5, 92, 92.5, 93,        93.5, 94, 94.5, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5, 99,        99.5, and about 100 weight percent.

In another suitable embodiment, said at least about 20 weight percentcis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or said at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or said at least about 20 weight percent of a mixturethereof is selected from a range defined by any two percentage numbersabove (inclusive of endpoints).

In one embodiment, the working fluid for extracting heat may consist ofHFO-1336mzz-Z. In another embodiment, the working fluid for extractingheat may consist of HFO-1336mzz-E. In another embodiment, the workingfluid for extracting heat may consist of a mixture of HFO-1336mzz-Z andHFO-1336mzz-E.

It is to be noted that at higher temperatures of operation thecis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z) in the working fluidmay undergo an isomerization to its trans isomer, that is,trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E). It was foundsurprisingly that such isomerization can be minimal even at highertemperatures such as 250° C.

The working fluid can also comprise less than about 80 weight percent ofone or more of other components selected from the following:

-   -   cis-HFO-1234ze; trans-HFO-1234ze; HFO-1234yf; HFO-1234ye-E or Z;        HFO-1225ye(Z); HFO-1225ye(E); HFO-1243zf        (3,3,3-trifluoropropene); HFO1225yc; HFO-1233zd-E or Z;        HFC-1233xf; CF₃CH═CHCF₃ (E); (CF₃)₂CFCH═CHF (E & Z);        (CF₃)₂CFCH═CF₂; CF₃CHFC═CHF (E & Z); (C₂F5)(CF₃)C═CH₂;        HFC-245fa; HFC-245eb; HFC-245ca; HFC-245cb; HFC-227ea;        HFC-236cb; HFC-236ea; HFC-236fa; HFC-365mfc; HFC-43-10mee;        CHF₂—O—CHF₂; CHF₂—O—CH₂F; CH₂F—O—CH₂F; CH₂F—O—CH₃;        cyclo-CF₂—CH₂—CF₂—O; cyclo-CF₂—CF₂—CH₂—O; CHF₂—O—CF₂—CHF₂;        CF₃—CF₂—O—CH₂F; CHF₂—O—CHF—CF₃; CHF₂—O—CF₂—CHF₂;        CH₂F—O—CF₂—CHF₂; CF₃—O—CF₂—CH₃; CHF₂—CHF—O—CHF₂; CF₃—O—CHF—CH₂F;        CF₃—CHF—O—CH₂F; CF₃—O—CH₂—CHF₂; CHF₂—O—CH₂—CF₃; CH₂F—CF₂—O—CH₂F;        CHF₂—O—CF₂—CH₃; CHF₂—CF₂—O—CH₃; CH₂F—O—CHF—CH₂F;        CHF₂—CHF—O—CH₂F; CF₃—O—CHF—CH₃; CF₃—CHF—O—CH₃; CHF₂—O—CH₂—CHF₂;        CF₃—O—CH₂—CH₂F; CF₃—CH₂—O—CH₂F; CF₂H—CF₂—CF₂—O—CH₃; propane;        cyclopropane; butane; isobutane; n-pentane; isopentane;        neopentane; cyclopentane; n-hexane; isohexane; heptane;        trans-1,2-dichloroethylene, and mixtures with cis-HFO-1234ze and        HFC-245fa.

In one embodiment of the above process, the working fluid comprises 80weight percent or less of at least one of the above compounds. Inanother embodiment, the working fluid comprises 70 weight percent orless of at least one of the above compounds. In another embodiment, theworking fluid comprises 60 weight percent or less of at least one of theabove compounds. In another embodiment, the working fluid comprises 50weight percent or less of at least one of the above compounds.

Note that while the working fluid in the process description above isidentified as a “first” working fluid and as a “second” working fluid,it should be understood that the difference between the two workingfluids is only that the first working fluid is what enters the ORCsystem while the second working fluid is the one that has undergone atleast one step of the process outlined in above.

In one embodiment of the above process, the temperature to which thefirst working fluid is heated in Step (b) is in the range of from about5° C. to about 400° C., preferably from about 150° C. to about 300° C.,more preferably from about 175° C. to 275° C., more preferably fromabout 200° C. to 250° C.

In a suitable embodiment, the temperature of operation at the expanderinlet can be any one of the following temperatures or within the range(inclusive) defined by any two numbers below:

-   -   about 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,        64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,        80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,        96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108,        109, 110, 111, 112, 113, 114, 115,        116,117,118,119,120,121,122,123,124, 125, 126, 127, 128, 129,        130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142,        143, 144, 145, 146, 147, 148, 149, 150, 151,152, 153, 154, 155,        156, 157, 158, 159, 160, 161, 162, and about 163, 164, 165, 166,        167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179,        180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192,        193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205,        206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218,        219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231,        232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244,        245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257,        258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270,        271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283,        284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296,        297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309,        310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 323,        323, 324, 325, 326, 327, 328, 329, 330, 331, 323, 333, 334, 335,        336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348,        349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, 361,        362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374,        375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387,        388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400°        C.

In one embodiment of the above process, the working fluid in Step (a) ispressurized in the range of from about 3 MPa to about 10 MPa. In asuitable embodiment, the pressure of operation can be any one of thefollowing pressures or within the range (inclusive) defined by any twonumbers below:

-   -   about 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0,        6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, and 10.0 MPa.

In one embodiment of the above process, said working fluid has a GWP ofless than 35. In a suitable embodiment, the GWP can be any one of thefollowing numbers or within the range (inclusive) defined by any twonumbers below:

-   -   5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12,        12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18,        18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24,        24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30,        30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, and about 35.

In the first step of the transcritical Organic Rankine Cycle (ORC)system, described above, the working fluid in liquid phase comprising atleast about 20 weight percent cis-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-Z), or at least about 20 weight percenttrans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), or at least about20 weight percent of a mixture thereof, is compressed to above itscritical pressure. The critical pressure of HFO-1336mzz-Z is 2.903 MPa;the critical pressure of HFO-1336mzz-E is 3.149 MPa. In a second step,said working fluid is passed through a heat exchanger to be heated to ahigher temperature before the fluid enters the expander wherein saidheat exchanger is in thermal communication with said heat source. Inother words, the heat exchanger receives heat energy from the heatsource by any known means of thermal transfer. The ORC system workingfluid circulates through the heat recovery heat exchanger where it gainsheat.

In the next step, at least a portion of the heated said first workingfluid is removed from said heat exchanger. The working fluid is routedto the expander where the expansion process results in conversion of atleast portion of the energy content of the working fluid into mechanicalenergy, often shaft energy. Shaft power can be used to do any mechanicalwork by employing conventional arrangements of belts, pulleys, gears,transmissions or similar devices depending on the desired speed andtorque required. In one embodiment, the shaft can also be connected toan electric power-generating device such as an induction generator. Theelectricity produced can be used locally or delivered to the grid. Thepressure on the working fluid is reduced to below critical pressure ofsaid working fluid, thereby rendering the working fluid to a firstworking fluid in vapor phase.

In the next step, the working fluid now in vapor phase is passed fromthe expander to a condenser, wherein the working fluid in vapor phase iscondensed to the working fluid in liquid phase. The above steps form aloop system and can be repeated many times.

Exemplar 1 Transcritical ORC: Totally Dry Expansion

FIG. 5 shows one embodiment of the present invention, wherein atranscritical ORC is used. FIG. 5 is a pressure-enthalpy diagram for thecycle of this embodiment. The substantially vertical lines on the plotare isentropic lines. The lines that are vertical on the left half ofthe curve but start showing deviation and curvature on the right half ofthe plot are isothermal lines. The broken line on the left side of thedome shape is the saturated liquid line. The broken line on the rightside of the dome shape is the saturated vapor line. In the first step,the working fluid is compressed (pressurized) above the criticalpressure of the working fluid usually substantially isentropically. Itis then heated under a substantially constant pressure (isobaric)condition to a temperature above its critical temperature. In the nextstep, the working fluid is expanded usually substantiallyisentropically. The fluid temperature is reduced during the expansionstep below its critical temperature. The fluid at the end of theexpansion step is in a superheated vapor state. In the next step, theworking fluid is cooled and condensed and heat is rejected and itstemperature is reduced. The working fluid passes through two phasechange boundaries, the saturated vapor curve, shown on the right side,and then the saturated liquid curve on the left. The working fluid is ina slightly subcooled liquid state at the end of this step.

Exemplar 2 Transcritical ORC; Partial Condensation During Expansion/DryVapor at Expander Exit

FIG. 6 shows one embodiment of the present invention, wherein atranscritical ORC is used. FIG. 6 is a pressure-enthalpy diagram for thecycle of this embodiment. The substantially vertical lines on the plotare isentropic lines. The lines that are vertical on the left half ofthe curve but start showing deviation and curvature on the right half ofthe plot are isothermal lines. The broken line on the left side of thedome shape is the saturated liquid line. The broken line on the rightside of the dome shape is the saturated vapor line. In the first step,the working fluid is compressed (pressurized) above the criticalpressure of the working fluid, usually substantially isentropically. Itis then heated under a substantially constant pressure condition to atemperature above its critical temperature.

The working fluid temperature is above its critical temperature only tosuch an extent that in the next step, when the working fluid is expandedusually substantially isentropically, and its temperature is reduced,the isentropic expansion approximately tracks the saturated vapor curvein such fashion that the expansion results in partial condensation ormisting of the working fluid. At the end of this expansion step,however, the working fluid is in a superheated vapor state, that is, itslocus is on the right side of the saturated vapor curve.

In the next step, the working fluid is cooled and condensed and heat isrejected and its temperature is reduced. The working fluid passesthrough two phase change boundaries, the saturated vapor curve, shown onthe right side, and then the saturated liquid curve on the left. Theworking fluid is in a slightly subcooled liquid state at the end of thisstep.

Exemplar 3 Transcritical ORC; Wet Expansion;T_(expander inlet)>T_(critical)

FIG. 7 shows one embodiment of the present invention, wherein atranscritical ORC is used. FIG. 7 is a pressure-enthalpy diagram for thecycle of this embodiment. The substantially vertical lines on the plotare isentropic lines. The lines that are vertical on the left half ofthe curve but start showing deviation and curvature on the right half ofthe plot are isothermal lines. The broken line on the left side of thedome shape is the saturated liquid line. The broken line on the rightside of the dome shape is the saturated vapor line.

In the first step, the working fluid is compressed (pressurized) abovethe critical pressure of the working fluid, usually substantiallyisentropically. It is then heated under a substantially constantpressure condition to a temperature only slightly above its criticaltemperature.

The working fluid temperature is above its critical temperature only tosuch an extent that in the next step, when the working fluid isexpanded, usually substantially isentropically, its temperature isreduced, and the isentropic expansion is a wet expansion. Specifically,the working fluid at the end of the expansion step is a vapor-liquidmixture.

In the next step, the working fluid is cooled, the vapor portion of theworking fluid is condensed and heat is rejected and its temperature isreduced. The working fluid in a vapor-liquid mixture passes through aphase change boundary at the saturated liquid curve. The working fluidis in a slightly subcooled liquid state at the end of this step.

Exemplar 4 Transcritical ORC: Wet Expansion:T_(expander inlet)<T_(critical)

FIG. 8 shows one embodiment of the present invention, wherein atranscritical ORC is used. FIG. 8 is a pressure-enthalpy diagram for thecycle of this embodiment. The substantially vertical lines on the plotare isentropic lines. The lines that are vertical on the left half ofthe curve but start showing deviation and curvature on the right half ofthe plot are isothermal lines. The broken line on the left side of thedome shape is the saturated liquid line. The broken line on the rightside of the dome shape is the saturated vapor line.

In the first step, the working fluid is compressed (pressurized) abovethe critical pressure of the working fluid, usually substantiallyisentropically. It is then heated under a substantially constantpressure condition to a temperature below its critical temperature.

In the next step, the working fluid is expanded, usually substantiallyisentropically, to a state of lower pressure and temperature at which itforms a vapor-liquid mixture (wet expansion).

In the next step, the working fluid is cooled, the vapor portion of theworking fluid is condensed and heat is rejected. The working fluid is ina slightly subcooled liquid state at the end of this step.

While the above exemplars show substantially isentropic, isenthalpic, orisothermal expansions and pressurizations, and isobaric heating orcooling, other cycles wherein such isentropic, isenthalpic, isothermal,or isobaric conditions are not maintained but the cycle is neverthelessaccomplished, are within the scope of the present invention.

One embodiment of the present invention relates to the Variable PhaseCycle or Trilateral Cycle (Phil Welch and Patrick Boyle: “New Turbinesto Enable Efficient Geothermal Power Plants” GRC Transactions, Vol. 33,2009). Liquid working fluid is pressurized and then heated in a heatexchanger with no vaporization. The heated, pressurized liquid leavingthe heat exchanger is directly expanded in a two-phase expander. The lowpressure fluid is condensed, closing the cycle.

In one embodiment, the present invention relates to a working fluidcomposition used in ORC systems to recover heat from heat sources,wherein the working fluid composition is maintained at a temperature inthe range of from about 175° C. to about 300° C., preferably from about200° C. to 250° C. and wherein the composition comprises at least about20 weight percent cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z),or at least about 20 weight percenttrans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), or at least about20 weight percent of a mixture thereof.

ORC Systems

In yet another embodiment, the present invention relates to ORC systemsusing the novel working fluid comprising at least about 20 weightpercent cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or at least about 20 weight percent of a mixturethereof. In another embodiment of the system, the working fluidcomprises at least 30 weight percent HFO-1336mzz-Z, HFO-1336mzz-E, ormixtures thereof. In another embodiment of the system, the working fluidcomprises at least weight percent HFO-1336mzz-Z, HFO-1336mzz-E, ormixtures thereof. In another embodiment of the system, the working fluidcomprises at least 50 weight percent HFO-1336mzz-Z, HFO-1336mzz-E, ormixtures thereof.

In one embodiment of the above system, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 10 weight percent HFO-1336mzz-E and 90 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises at least about 15 weight percentHFO-1336mzz-E and 85 or more weight percent HFO-1336mzz-Z.

In another embodiment, wherein the working fluid comprises a mixture ofHFO-1336mzz-Z and HFO-1336mzz-E, the working fluid comprises at leastabout 20 weight percent HFO-1336mzz-E and 80 or more weight percentHFO-1336mzz-Z. In another embodiment, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 25 weight percent HFO-1336mzz-E and 75 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises from about 25 weight percent to about 75weight percent HFO-1336mzz-E and from about 75 weight percent to about25 weight percent HFO-1336mzz-Z.

In one embodiment, the working fluid in the ORC system may consist ofHFO-1336mzz-Z. In another embodiment, the working fluid in the ORCsystem may consist of HFO-1336mzz-E. In another embodiment, the workingfluid in the ORC system may consist of a mixture of HFO-1336mzz-Z andHFO-1336mzz-E.

In another embodiment, the present invention includes an Organic RankineCycle System extracting heat at an operating pressure in the range ofabout 3 MPa to about 10 MPa, wherein said system contains a workingfluid, and wherein about 50 weight percent of said working fluidcomprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.

The novel working fluid of the present invention may be used in an ORCsystem to extract thermal energy and convert it to mechanical energyfrom heat sources such as low pressure steam, low grade thermal energysources such as industrial waste heat, solar energy, geothermal hotwater, low-pressure geothermal steam (primary or secondary arrangements)or distributed power generation equipment utilizing fuel cells or primemovers such as turbines, microturbines, or internal combustion engines.Low-pressure steam can also be accessed in a process known as a binaryRankine cycle. Large quantities of low-pressure steam can be found innumerous locations, such as in fossil fuel powered electrical generatingpower plants. The working fluid of the present invention can be tailoredto suit the power plant coolant quality (its temperature), maximizingthe efficiency of the binary cycle.

Other sources of heat include waste heat recovered from gases exhaustedfrom mobile internal combustion engines (e.g. truck or rail or shipDiesel engines), aircraft engines, waste heat from exhaust gases fromstationary internal combustion engines (e.g. stationary Diesel enginepower generators), waste heat from fuel cells, heat available atCombined Heating, Cooling and Power or District Heating and Coolingplants, waste heat from biomass fueled engines, heat from natural gas ormethane gas burners or methane-fired boilers or methane fuel cells (e.g.at distributed power generation facilities) operated with methane fromvarious sources including biogas, landfill gas and coal bed methane,heat from combustion of bark and lignin at paper/pulp mills, heat fromincinerators, heat from low pressure steam at conventional steam powerplants to drive “bottoming” Rankine cycles with a composition that is atleast about 20 weight percent cis-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-Z), or at least about weight percenttrans-1,1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), or at leastabout 20 weight percent of a mixture thereof as the working fluid,geothermal heat to Rankine cycles with a composition that is at leastabout 20 weight percent cis-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-Z), or at least about 20 weight percenttrans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), or at least about20 weight percent of a mixture thereof as the working fluid circulatingabove ground (e.g. binary cycle geothermal power plants), geothermalheat to Rankine cycles with HFO-1336mzz-Z or HFO-1336mzz-E or mixturesof HFO-1336mzz-Z and HFO-1336mzz-E as the Rankine cycle working fluidand as a geothermal heat carrier circulating underground in deep wellswith the flow largely or exclusively driven by temperature-induced fluiddensity variations, known as “the thermosiphon effect” (e.g. see Davis,A. P. and E. E. Michaelides: “Geothermal power production from abandonedoil wells”, Energy, 34 (2009) 866-872; Matthews, H. B. U.S. Pat. No.4,142,108—Feb. 27, 1979) solar heat from solar panel arrays includingparabolic solar panel arrays, solar heat from Concentrated Solar Powerplants, heat removed from photovoltaic (PV) solar systems to cool the PVsystem to maintain a high PV system efficiency. In other embodiments,the present invention also uses other types of ORC systems, for example,small scale (e.g. 1-500 kw, preferably 5-250 kw) Rankine cycle systemsusing micro-turbines or small size positive displacement expanders (e.g.Tahir, Yamada and Hoshino: “Efficiency of compact organic Rankine cyclesystem with rotary-vane-type expander for low-temperature waste heatrecovery”, Int'l. J. of Civil and Environ. Eng 2:1 2010), combined,multistage, and cascade Rankine Cycles, and Rankine Cycle systems withrecuperators to recover heat from the vapor exiting the expander.

Other sources of heat include at least one operation associated with atleast one industry selected from the group consisting of: oilrefineries, petrochemical plants, oil and gas pipelines, chemicalindustry, commercial buildings, hotels, shopping malls, supermarkets,bakeries, food processing industries, restaurants, paint curing ovens,furniture making, plastics molders, cement kilns, lumber kilns,calcining operations, steel industry, glass industry, foundries,smelting, air-conditioning, refrigeration, and central heating.

Methods for Replacing HFC-245Fa in ORC Systems

Currently used ORC systems utilizing HFC-245fa may be in need of a newworking fluid with lower global warming potential (GWP). The GWP ofHFC-245fa is 1030. The GWP for working fluids of the present inventionare considerably lower. HFO-1336mzz-Z has a GWP of 9.4, whileHFO-1336mzz-E has a GWP of about 32. Thus, many working fluids may beformulated that provide more environmentally sustainable working fluidsfor ORC systems using HFO-1336mzz-Z, HFO-1336mzz-E or mixtures thereof.

In one embodiment is provided a method for replacing HFC-245fa in apower cycle system comprising removing said HFC-245fa from said powercycle system and charging said system with a replacement working fluidcomprising at least about 20 weight percent of HFO-1336mzz-Z,HFO-1336mzz-E, or mixtures thereof. In another embodiment, thereplacement working fluid comprises at least 30 weight percentHFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In anotherembodiment, the replacement working fluid comprises at least 40 weightpercent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In anotherembodiment, the replacement working fluid comprises at least 50 weightpercent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.

In one embodiment of the above process, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 10 weight percent HFO-1336mzz-E and 90 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises at least about 15 weight percentHFO-1336mzz-E and 85 or more weight percent HFO-1336mzz-Z. In anotherembodiment, wherein the working fluid comprises a mixture ofHFO-1336mzz-Z and HFO-1336mzz-E, the working fluid comprises at leastabout 20 weight percent HFO-1336mzz-E and 80 or more weight percentHFO-1336mzz-Z. In another embodiment, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 25 weight percent HFO-1336mzz-E and 75 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises from about 25 weight percent to about 75weight percent HFO-1336mzz-E and from about 75 weight percent to about25 weight percent HFO-1336mzz-Z.

The working fluid described above comprises at least about 20 weightpercent cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or at least about 20 weight percent of a mixturethereof. In another embodiment, the working fluid comprises at least 30weight percent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. Inanother embodiment, the working fluid comprises at least 40 weightpercent HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In anotherembodiment, the working fluid comprises at least 50 weight percentHFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. In a suitableembodiment, said at least about 20 weight percentcis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or said at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or said at least about 20 weight percent of a mixturethereof is selected from the following percentage content of the workingfluid:

-   -   about 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,        34, 35, 36, 37, 38, 39, 40, 41,42, 43, 44, 45, 46, 47, 48, 49,        50, 50.5, 51, 52, 52.5, 53, 53.5, 54, 54.5, 55, 55.5, 56, 56.5,        57, 57.5, 58, 58.5, 59, 59.5, 60, 60.5, 61, 61.5, 62, 62.5, 63,        63.5, 64, 64.5, 65, 65.5, 66, 66.5, 67, 67.5, 68, 68.5, 69,        69.5, 70, 70.5, 71, 71.5, 72, 72.5, 73, 73.5, 74, 74.5, 75,        55.5, 76, 76.5, 77, 77.5, 78, 78.5, 79, 79.5, 80, 80.5, 81,        81.5, 82, 82.5, 83, 83.5, 84, 84.5, 85, 85.5, 86, 86.5, 87,        87.5, 88, 88.5, 89, 89.5, 90, 90.5, 91, 91.5, 92, 92.5, 93,        93.5, 94, 94.5, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5, 99,        99.5, and about 100%.

In another suitable embodiment, said at least about 20 weight percentcis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), or said at leastabout 20 weight percent trans-1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz-E), or said at least about 20 weight percent of a mixturethereof is selected from a range defined by any two percentage numbersabove (inclusive of endpoints).

In one embodiment of the above process, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 10 weight percent HFO-1336mzz-E and 90 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises at least about 15 weight percentHFO-1336mzz-E and 85 or more weight percent HFO-1336mzz-Z. In anotherembodiment, wherein the working fluid comprises a mixture ofHFO-1336mzz-Z and HFO-1336mzz-E, the working fluid comprises at leastabout 20 weight percent HFO-1336mzz-E and 80 or more weight percentHFO-1336mzz-Z. In another embodiment, wherein the working fluidcomprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E, the workingfluid comprises at least about 25 weight percent HFO-1336mzz-E and 75 ormore weight percent HFO-1336mzz-Z. In another embodiment, wherein theworking fluid comprises a mixture of HFO-1336mzz-Z and HFO-1336mzz-E,the working fluid comprises from about 25 weight percent to about 75weight percent HFO-1336mzz-E and from about 75 weight percent to about25 weight percent HFO-1336mzz-Z.

The working fluid can also comprise less than about 80 weight percent ofone or more of other components selected from the following:cis-HFO-1234ze; trans-HFO-1234ze; HFO-1234yf; HFO-1234ye-E or Z; HFO1225ye(Z); HFO-1225ye(E); HFO-1225yc; HFO-1243zf(3.3.3-trifluoropropene); HFO-1233zd-E or Z; HFO-1233xf; CF₃CH═CHCF₃(E); (CF₃)₂CFCH═CHF (E & Z); (CF₃)₂CFCH═CF₂; CF₃CHFC═CHF (E & Z);(C₂F5)(CF₃)C═CH₂; HFC-245fa; HFC-245eb; HFC-245ca; HFC-245cb; HFC-227ea;HFC-236cb; HFC-236ea; HFC-236fa; HFC-365mfc; HFC-43-10mee; CHF₂—O—CHF₂;CHF₂—O—CH₂F; CH₂F—O—CH₂F; CH₂F—O—CH₃; cyclo-CF₂—CH₂—CF₂—O;cyclo-CF₂—CF₂—CH₂—O; CHF₂—O—CF—CHF₂; CF₃—CF₂—O—CH₂F; CHF₂—O—CHF—CF₃;CHF₂—O—CF₂—CHF₂; CH₂F—O—CF₂—CHF₂; CF₃—O—CF₂—CH₃; CHF₂—CHF—O—CHF₂;CF₃—O—CHF—CH₂F; CF₃—CHF—O—CH₂F; CF₃—O—CH₂—CHF₂; CHF₂—O—CH₂—CF₃;CH₂F—CF₂—O—CH₂F; CHF₂—O—CF₂—CH₃; CHF₂—CF₂—O—CH₃; CH₂F—O—CHF—CH₂F;CHF₂—CHF—O—CH₂F; CF₃—O—CHF—CH₃; CF₃—CHF—O—CH₃; CHF₂—O—CH₂—CHF₂;CF₃—O—CH₂—CH₂F; CF₃—CH₂—O—CH₂F; CF₂H—CF₂—CF₂—O—CH₃; propane;cyclopropane; butane; isobutane; n-pentane; isopentane; neopentane;cyclopentane; n-hexane; isohexane; heptane; trans-1,2-dichloroethylene,and mixtures with cis-HFO-1234ze and HFC-245fa.

In one embodiment, the working fluid comprises 80 weight percent or lessof at least one of the above compounds. In another embodiment, theworking fluid comprises 70 weight percent or less of at least one of theabove compounds. In another embodiment, the working fluid comprises 60weight percent or less of at least one of the above compounds. Inanother embodiment, the working fluid comprises 50 weight percent orless of at least one of the above compounds.

In one embodiment, the working fluid for extracting heat may consist ofHFO-1336mzz-Z. In another embodiment, the working fluid for extractingheat may consist of HFO-1336mzz-E. In another embodiment, the workingfluid for extracting heat may consist of a mixture of HFO-1336mzz-Z andHFO-1336mzz-E.

EXAMPLES

The concepts described herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

Example A

Example A demonstrates the generation of power from diesel engineexhaust heat using Rankine Cycles with HFO-1336mzz-Z under subcriticalconditions wherein the evaporation temperature T_(evap) is less than thecritical temperature of HFO-1336mzz-Z (T_(cr) _(—)_(HFO-1336mzz-Z)=171.28° C.).

Mechanical power generation from heat extracted from the exhaust gasesof internal combustion engines (e.g. Diesel engines) using Rankine cyclesystems with HFO-1336mzz-Z as the working fluid is illustrated in theexamples below. The mechanical power generated through the Rankine cycleis in addition to the mechanical power generated by the engine from fuelcombustion and increases the overall amount of mechanical powergenerated per unit of fuel mass combusted.

The performance of the working fluid comprising HFO-1336mzz-Z(CF₃CH═CHCF₃) is compared with the performance of the well-known workingfluid HFC-245fa (CHF₂CH₂CF₃).

Example A1 Low Temperature Operation (T_(evaporator)=132.22° C.)

Evaporator (boiler) T_(evaporator) = 270° F. = 132.22° C. temperature:Condenser temperature: T_(condenser) = 130° F. = 54.44° C. Superheat ofvapor ΔT_(suph) = 36° F. = 20° C. entering the expander: LiquidSub-cooling: ΔT_(subc) = 14° F. = 7.78° C. Expander Efficiency η_(exp) =0.85 Pump Efficiency η_(pump) = 0.85

TABLE A1 HFO-1336mzz-Z HFO- vs HFC-245fa 1336mzz-Z HFC-245fa % GWP_1001030 9.4 T_(evap) ° C. 132.22 132.22 T_(cond) ° C. 54.44 54.44 ΔT_(suph)° C. 20 20 ΔT_(subc) ° C. 7.78 7.78 EFF_expn 0.85 0.85 EFF_comp 0.850.85 P_(evap) MPa 2.45 1.41 −42.21 P_(cond) MPa 0.39 0.21 −47.50 EFF0.1142 0.1141 −0.09 CAP kJ/m3 543.63 311.86 −42.63

Table A1 shows that HFO-1336mzz-Z virtually matches the energyefficiency of HFC-245fa while offering a much lower GWP. Moreover,HFO-1336mzz-Z generates substantially lower operating pressures thanHFC-245fa. (However, the volumetric capacity of HFO-1336mzz-Z togenerate power, CAP, is lower than HFC-245fa.

The thermodynamic efficiency of the Rankine cycle operating withHFO-1336mzz-Z, 11.41%, virtually matches that of HFC-245fa at the samecycle operating conditions. The evaporator pressure with HFO-1336mzz-Z(1.41 MPa) is substantially lower than with HFC-245fa (2.45 MPa). (Ahigher volumetric flow rate at the expander exit is required to generatea target mechanical power rate with HFO-1336mzz-Z than with HFC-245fa.Equivalently, a lower amount of mechanical work is generated when a unitof HFO-1336mzz-Z volume is circulated through the cycle (311.86 kJ/m3)than HFC-245fa (543.63 kJ/m³).

Example A2 High Temperature Operation (T_(evaporator)=155° C.)

HFO-1336mzz-Z has a higher critical temperature (see Table A2) andgenerates lower vapor pressures than HFC-245fa. As a result,HFO-1336mzz-Z can enable sub-critical Organic Rankine cycle operation athigher temperatures than HFC-245fa (see Table A3).

TABLE A2 Critical point of HFO-1336mzz-Z compared to HFC-245faHFO-1336mzz-Z HFC-245fa T_(cr) ° C. 171.28 154 P_(cr) MPa 2.903 3.650

TABLE A3 Rankine Cycle with HFO-1336mzz-Z at Tevap = 155° C. vs 132.22°C. T_(evap) = 155° C. HFO-1336mzz- HFO- versus Z at T_(evap) = 1336mzz-Zat T_(evap) = 132.22° C. T_(evap) = 155° C. 132.22° C.; % T_(evap) ° C.132.22 155 T_(cond) ° C. 54.44 54.44 ΔT_(suph) ° C. 20 20 ΔT_(subc) ° C.7.78 7.78 EFF_expn 0.85 0.85 EFF_comp 0.85 0.85 P_(evap) MPa 1.41 2.1854.11 P_(cond) MPa 0.21 0.21 0.00 EFF_thermal 0.1141 0.1311 14.90 CAP_ekJ/m³ 311.86 369.64 18.53

HFO-1336mzz-Z can be used as a working fluid for a subcritical OrganicRankine cycle operating with a heat source that allows the evaporator toreach a temperature of 155° C. (i.e. higher than the criticaltemperature of HFC-245fa). Table A3 shows that an evaporator temperatureof 155° C. leads to substantially improved efficiency and volumetriccapacity for power generation (by 14.90% and 18.53%, respectively)relative to an evaporating temperature of 132.22° C.

Example A3 High Temperature Operation (T_(evaporator)=161.60° C.)

HFO-1336mzz-Z generates lower vapor pressures than HFC-245fa at a giventemperature. Therefore, for any given maximum permissible evaporatorworking pressure, HFO-1336mzz-Z can enable Organic Rankine Cyclesoperating at higher evaporator temperatures than HFC-245fa. Table A4compares an Organic Rankine Cycle with HFO-1336mzz-Z and an evaporatortemperature of 161.6° C. to an Organic Rankine Cycle with HFC-245fa andan evaporator temperature of 132.22° C. Both cycles operate with anevaporator operating pressure of 2.45 MPa. The cycle operating withHFO-1336mzz-Z achieves higher energy efficiency (13.51%) than HFC-245fa(11.42%).

TABLE A4 Rankine Cycle with HFO-1336mzz-Z vs HFC-245fa at P_(evap) =2.45 MPa HFC- HFO- HFO-1336mzz-Z 245fa 1336mzz-Z Vs HFC-245fa; in %T_(evap) ° C. 132.22 161.6 T_(cond) ° C. 54.44 54.44 ΔT_(suph) ° C. 2020 ΔT_(subc) ° C. 7.78 7.78 EFF_expn 0.85 0.85 EFF_comp 0.85 0.85P_(evap) MPa 2.45 2.45 P_(cond) MPa 0.39 0.21 −47.50 EFF_thermal 0.11420.1351 18.30 CAP_e kJ/m³ 543.63 383.86 −29.39

Example B

Example B demonstrates the generation of power from diesel engineexhaust heat using Rankine Cycles with HFO-1336mzz-Z under transcriticalconditions.

Surprisingly, HFO-1336-mzz-Z remains chemically stable at temperaturessubstantially higher than its critical temperature (of 171.28° C.).Therefore, HFO-1336-mzz-Z can enable Rankine cycles that harvest heatsources with temperatures higher than 171.28° C. using HFO-1336-mzz-Z asthe working fluid in a supercritical state. Use of higher temperatureheat sources leads to higher cycle energy efficiencies and volumetriccapacities for power generation (relative to the use of lowertemperature heat sources).

When a supercritical fluid heater is used instead of the evaporator (orboiler) of the conventional subcritical Rankine cycle, the heaterpressure and the heater exit temperature (or equivalently the expanderinlet temperature) must be specified. FIG. 3 shows the energy efficiencyof a transcritical Rankine cycle operating with HFO-1336mzz-Z as theworking fluid as a function of the pressure of the supercritical fluidheater and the temperature of the working fluid at the expander inlet.For example, operating the supercritical fluid heater at a pressure of 5MPa and a heater exit temperature (or expander inlet temperature) of225° C. achieves a Rankine cycle energy efficiency of 15.5%. At higherexpander inlet temperatures, maximum efficiency is achieved atincreasingly higher heater pressures. Higher operating pressures in thesupercritical fluid heater would necessitate the use of more robustequipment.

Often the temperature of the heat source diminishes during the heatexchange process. In the case of sub-critical Rankine cycle operation,the working fluid temperature is constant throughout the heat extractionevaporation process. The use of a supercritical fluid to extract heatallows better matching between the varying temperatures of the heatsource and of the supercritical working fluid relative to the case ofsub-critical operation. As a result, the effectiveness of the heatexchange process for the transcritical cycle can be higher than that ofthe sub-critical cycle (see Chen et al, Energy, 36, (2011) 549-555 andreferences therein).

Example B1 Transcritical Organic Rankine Cycle with T_(expander in)=200or 250° C.

TABLE B1 Performance of transcritical Organic Rankine Cycles withHFO-1336mzz-Z as the working fluid at two selected sets of conditions Aand B HFO- HFO- 1336mzz-Z 1336mzz-Z units A B A vs B; in % P_(heater)MPa 3 6 T_(expn)_in ° C. 200 250 T_(cond) ° C. 54.44 54.44 ΔT_(subc) °C. 7.78 7.78 EFF_expn 0.85 0.85 EFF_comp 0.85 0.85 P_(cond) MPa 0.210.21 EFF_thermal 0.142 0.161 13.38 CAP_e kJ/m³ 412.03 493.83 19.85

Table B1 shows that a Rankine cycle first heating HFO-1336mzz-Z at 3 MPato 200° C. then expanding the heated HFO-1336mzz-Z to the operatingpressure (0.21 MPa) of the condenser at Tcond=54.44° C. achieves athermal efficiency of 14.2% and a volumetric capacity for powergeneration of 412.03 kJ/m³. Even higher efficiency and volumetriccapacity for power generation can be achieved when the working fluid,HFO-1336mzz-Z, is heated to 250° C. at a pressure of 6 MPa.HFO-1336mzz-Z remains sufficiently stable at 250° C. Higher efficienciesand capacities are achieved with the transcritical cycles vs thesubcritical cycles in example A. Table B2 compares the performance of atranscritical Rankine cycle with HFO-1336mzz-Z as the working fluid toHFC-245fa for the same fluid heater pressure, heater exit temperature,condenser temperature, liquid sub-cooling, expander efficiency andliquid compressor (i.e. pump) efficiency.

TABLE B2 Performance of a transcritical Rankine cycle with HFO-1336mzz-Zas the working fluid compared to HFC-245fa HFC- HFO- HFO-1336mzz-Z vs245fa 1336mzz-Z HFC-245fa; in % P_(heater) MPa 6 6 T_(expn)_in ° C. 250250 T_(cond) ° C. 54.44 54.44 ΔT_(subc) ° C. 7.78 7.78 EFF_expn 0.850.85 EFF_comp 0.85 0.85 P_(cond) MPa 0.39 0.21 −47.50 EFF_thermal 0.1490.161 8.05 CAP_e kJ/m³ 801.92 493.83 −38.42

Example C1 Sub-Critical ORC with HFO-1336mzz-Z at an Evaporator Pressureof 2.18 MPa

Table C1 shows that HFO-1336mzz-Z could enable Organic Rankine cyclesassembled with widely available relatively low cost HVAC-type equipmentoperating at moderate evaporator pressures (not exceeding about 2.18MPa) while also offering attractive safety, health, and environmentalproperties and attractive energy efficiencies. Using low cost equipmentsubstantially expands the practical applicability of ORCs (see Joost J.Brasz, Bruce P. Biederman and Gwen Holdmann: “Power Production from aModerate-Temperature Geothermal Resource”, GRC Annual Meeting, Sep.25-28th, 2005; Reno, Nev., USA). Table C1 shows that the energyefficiency enabled by HFO-1336mzz-Z, 15.51%, is 15.06% higher than theenergy efficiency, 13.48%, enabled by HFC-245fa.

TABLE C1 Safety, health, environmental and ORC performance properties ofHFO-1336mzz-Z for an evaporating pressure equal to 2.18 MPa compared toHFC-245fa. units HFO-1336mzz-Z HFC-245fa ASHRAE Standard 34 A B ToxicityClass (expected) ASHRAE Standard 34 1 1 Flammability Class (expected)OEL, ppmv 500 300 (expected) Atmospheric Life Time [yrs] 0.0658 7.6 (24days) ODP None None GWP (100 year horizon) 9.4 1030 Tevap ° C. 155 126.2Tcond ° C. 40 40 □Tsuph ° C. 0 0 □Tsubc ° C. 0 0 EFF_expn 0.85 0.85EFF_comp 0.85 0.85 Pevap MPa 2.18 2.18 Pcond MPa 0.13 0.25 Texpn_out °C. 81.56 65.50 EFF_thermal 0.1551 0.1348

Example C2 Transcritical ORC Operating with HFO-1336mzz-Z as the WorkingFluid

The Rankine cycle energy efficiency with an expander inlet temperatureof 250° C. increases monotonically with heater pressure increasing fromabove critical pressure to 9 MPa for both HFO-1336mzz-Z and HFC-245fa.The selected heater pressure (9 MPa) in Table C2 is higher than themaximum working pressure of most commonly available HVAC type equipment.

Table C2 shows that HFO-1336mzz-Z could enable transcritical Rankinecycle systems to convert heat available at relatively high temperatures(250° C.) to power with energy efficiency 2.7% higher than HFC-245fa (atthe same operating conditions) while offering more attractive safety andenvironmental properties.

Tables C1 and C2 show that transcritical Rankine cycle systems withHFO-1336mzz-Z, used to convert heat available at relatively hightemperatures (250° C.) to power, can achieve higher energy efficiencythan subcritical ORCs operating with HFO-1336mzz-Z.

TABLE C2 Performance of a transcritical ORC operating with HFO-1336mzz-Zat a supercritical fluid heater pressure of 9 MPa and an expander inlettemperature of 250° C. compared to HFC-245fa. units HFO-1336mzz-ZHFC-245fa P_heater MPa 9 9 Texpn_in ° C. 250 250 Tcond ° C. 40 40 ΔTsubc° C. 0 0 EFF_expn 0.85 0.85 EFF_comp 0.85 0.85 Pcond MPa 0.128 0.250EFF_thermal 0.187 0.182

Example C3 Supercritical Fluid Heater Pressures that Maximize EnergyEfficiency of Rankine Cycle Operating with HFO-1336mz-Z for SelectedExpander Inlet Temperatures

FIG. 4 shows energy efficiency as function of heater pressure atdifferent expander inlet temperatures. It was surprisingly found thatthe energy efficiency increased with heater pressure at higher expanderinlet temperatures. The efficiency at 10 MPa for an expander temperatureof 250° C. was found to be greater than 18%.

Example C4 Chemical Stability of HFO-1336mzz-Z

The chemical stability of HFO-1336mzz-Z in the presence of metals wasscrutinized according to the sealed tube testing methodology ofANSI/ASHRAE Standard 97-2007. The stock of HFO-1336mzz-Z used in thesealed tube tests was 99.9864+ weight percent pure (136 ppmw ofimpurities) and contained virtually no water or air.

Sealed glass tubes, each containing three metal coupons made of steel,copper, and aluminum immersed in HFO-1336mzz-Z, were aged in a heatedoven at various temperatures up to 250° C. for 14 days. Visualinspection of the tubes after thermal aging indicated clear liquids withno discoloration or other visible deterioration of the fluid. Moreover,there was no change in the appearance of the metal coupons indicatingcorrosion or other degradation.

Table C3 shows the measured concentrations of fluoride ion in the agedliquid samples. The fluoride ion concentration can be interpreted as anindicator of the degree of HFO-1336mzz-Z degradation. Table C3 indicatesthat HFO-1336mzz-Z degradation was surprisingly minimal even at thehighest temperature tested (250° C.).

TABLE C3 Fluoride ion concentration in HFO-1336mzz-Z samples after agingat various temperatures for two weeks. Aging Temperature F-ion [° C.][ppmm] 175 <0.15(*) 200 0.18 225 0.23 250 1.50 (*)no detectable fluoride(within the method detection limit of 0.15 ppm)

Table C4 shows compositional changes, quantified by GCMS, ofHFO-1336mzz-Z samples after aging in the presence of steel, copper andaluminum at various temperatures for two weeks. Only negligibleproportions of new unknown compounds appeared as a result of aging evenat the highest temperature tested (250° C.).

The trans isomer of HFO-1336mzz, HFO-1336mzz-E, is expected to bethermodynamically more stable than the cis isomer, HFO-1336mzz-Z, byabout 5 kcal/mole. Surprisingly, despite the substantial thermodynamicdriving force for isomerization of HFO-1336mzz-Z to the more stabletrans isomer, the measured results in Table C4 indicate thatHFO-1336mzz-Z remained largely in the Z (or cis) isomeric form even atthe highest temperature tested (250° C.). The effect of the smallproportion (3,022.7 ppm or 0.30227 weight percent) of HFO-1336mzz-E thatformed after two weeks of aging at 250° C. on the thermodynamicproperties of the working fluid (HFO-1336mzz-Z) and, therefore on thecycle performance, would be negligible.

TABLE C4 Compositional changes of HFO-1336mzz-Z samples (quantified byGCMS) after aging in the presence of steel, copper and aluminum couponsat various temperatures for two weeks. Unknown compounds HFO-1336mzz-E(formed as a result of Aging [ppm] aging) Temperature (by GC peak [ppm][° C.] area) (by GC peak area) Initial stock of HFO- Not present Notpresent 1336mzz-Z (unaged) 150 23.8 0.5 175 38.7 4.0 200 116.6 25.0 225343.4 77.1 250 3,022.7 425.5

Example D Sub-Critical ORC with HFO-1336mzz-E at an Evaporator Pressureof 2.18 MPa

Table D compares the performance of a subcritical Rankine cycleoperating with HFO-1336mzz-E as the working fluid to subcritical Rankinecycles operating with HFO-1336mzz-Z or HFC-245fa as the working fluids.The evaporator pressure for all cycles compared in Table D is 2.18 MPa.The cycle energy efficiency with HFO-1336mzz-E is 8.46% lower than thatwith HFC-245fa. The volumetric capacity for power generation withHFO-1336mzz-E is 8.6% higher than that with HFC-245fa.

The performance of HFC-245fa is bracketed by the performance ofHFO-1336mzz-Z and HFO-1336mzz-E. This suggest that blends ofHFO-1336mzz-Z and HFO-1336mzz-E could be formulated to replace HFC-245fain existing Rankine Cycle applications.

TABLE D Safety, health, environmental and ORC performance properties ofHFO-1336mzz-E for an evaporating pressure equal to 2.18 MPa compared toHFO-1336mzz-Z and HFC-245fa. HFO- HFC- HFO- units 1336mzz-Z 245fa1336mzz-E ASHRAE Standard 1 1 1 34 Flammability (expected) (expected)Class ODP None None None GWP (100 year 9.4 1030 32 horizon) Tevap ° C.155 126.2 118.20 Tcond ° C. 40 40 40 ΔTsuph ° C. 0 0 0 ΔTsubc ° C. 0 0 0EFF_expn 0.85 0.85 0.85 EFF_comp 0.85 0.85 0.85 Pevap MPa 2.18 2.18 2.18Pcond MPa 0.13 0.25 0.32 Texpn_out ° C. 81.56 65.50 60.90 EFF_thermal0.1551 0.1348 0.1234 CAP_e (Volumetric kJ/m³ 272.2 409.9 445.1 Capacityfor power generation)

Example E Sub-Critical ORC with HFO-1336mzz-E at an EvaporatorTemperature of 120° C.

Table E compares the performance of a Rankine cycle with HFO-1336mzz-Eat an evaporating temperature of 120° C. to HFO-1336mzz-Z and HFC-145fa.The cycle energy efficiency with HFO-1336mzz-E is 3.8% lower than thatwith HFC-245fa. The volumetric capacity for power generation withHFO-1336mzz-E is 16.2% higher than that with HFC-245fa.

The performance of HFC-245fa is bracketed by the performance ofHFO-1336mzz-Z and HFO-1336mzz-E. This suggests that blends ofHFO-1336mzz-Z and HFO-1336mzz-E could be formulated to replace HFC-245fain existing Rankine Cycle applications.

TABLE E Subcritical ORC performance with HFO-1336mzz-E at an evaporatingtemperature of 120° C. HFO- HFC- HFO- units 1336mzz-Z 245fa 1336mzz-ETevap ° C. 120 120 120 Tcond ° C. 35 35 35 ΔTsuph ° C. 0 0 0 ΔTsubc ° C.0 0 0 EFF_expn 0.85 0.85 0.85 EFF_comp 0.85 0.85 0.85 Pevap Mpa 1.101.93 2.26 Pcond Mpa 0.11 0.21 0.27 Texpn_out ° C. 70.94 61.28 57.55EFF_thermal 0.1376 0.1372 0.1320 CAP_e (Volumetric kJ/m³ 200.46 361.47420.07 Capacity for power generation)

Example F Sub-Critical ORC with an HFO-1336mzz-E/HFO-1336mzz-Z Blend asthe Working Fluid

Table F summarizes the performance of Rankine cycles withHFO-1336mzz-E/HFO-1336mzz-Z blends of three different compositions. Thecomposition of HFO-1336mzz-E/HFO-1336mzz-Z blends can be varied toachieve different performance targets.

TABLE F Performance of subcritical ORCs with HFO-1336mzz-E/HFO-1336mzz-Z blends of different compositions units Blend A Blend BBlend C HFO-1336mzz-Z wt % 75 50 25 HFO-1336mzz-E wt % 25 50 75Tevap_average ° C. 120 120 120 Tcond_average ° C. 35 35 35 ΔTsuph ° C. 00 0 ΔTsubc ° C. 0 0 0 EFF_expn 0.85 0.85 0.85 EFF_comp 0.85 0.85 0.85Pevap MPa 1.35 1.63 1.94 Pcond MPa 0.14 0.18 0.22 Texpn_out ° C. 70.8768.04 63.37 EFF_thermal 0.1333 0.1327 0.1327 CAP_e (Volumetric kJ/m³253.39 306.31 362.55 Capacity for power generation)

Example G Transcritical ORC with HFO-1336mzz-E

Table G compares the performance transcritical ORCs with HFO-1336mzz-E,HFO-1336mzz-Z, a 50/50 wt % blend of HFO-1336mzz-E and HFO-1336mzz-Z,and HFC-245fa.

TABLE G transcritical ORC performance with HFO-1336mzz-E HFO-1336mzz-HFO- HFC- HFO- E/HFO-1336mzz-Z units 1336mzz-Z 245fa 1336mzz-E 50/50 wt% P_heater MPa 4 4 4 4 Texpn_in ° C. 200 200 200 200 Tcond ° C. 35 35 3535 ΔTsubc ° C. 0 0 0 0 EFF_expn 0.85 0.85 0.85 0.85 EFF_comp 0.85 0.850.85 0.85 Pcond MPa 0.11 0.21 0.27 0.18 EFF_thermal 0.176 0.165 0.1530.163 CAP_e (Volumetric kJ/m³ 278.46 479.45 554.93 416.73 Capacity forpower generation)

From the data it has been demonstrated that HFO-1336mzz-Z and mixturesthereof with HFO-1336mzz-E provide efficiencies close to that ofHFC-245fa. Additionally, adding HFO-1336mzz-E to HFO-1336mzz-Z allowsthe use of such mixture which may provide a volumetric capacity forpower generation to approach that for HFC-245fa, while providing a moreenvironmentally sustainable working fluid for the industry.

1. A process for recovering heat from a heat source and generatingmechanical energy, comprising the steps of: (a) passing a first workingfluid in liquid phase through a heat exchanger or an evaporator, whereinsaid heat exchanger or said evaporator is in communication with saidheat source that supplies said heat; (b) removing at least a portion ofsaid first working fluid in a vapor phase from said heat exchanger orsaid evaporator; (c) passing said at least a portion of said firstworking fluid in vapor phase to an expander, wherein at least portion ofsaid heat is converted into mechanical energy; (d) passing said at leasta portion of said first working fluid in vapor phase from said expanderto a condenser, wherein said at least a portion of said first workingfluid in vapor phase is condensed to a second working fluid in liquidphase; (e) optionally, compressing and mixing said second working fluidin liquid phase with said first working fluid in liquid phase in Step(a); and (f) optionally, repeating Steps (a) through (e), at least onetime; wherein at least about 20 weight percent of said first workingfluid comprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof. 2.The process as recited in claim 1, wherein the efficiency of convertingheat to mechanical energy (cycle efficiency) is at least about 7%. 3.The process as recited in claim 1, wherein the evaporator operatingtemperature is less than or equal to about 171° C.
 4. The process asrecited in claim 1, wherein the evaporator operating pressure is lessthan about 2.5 MPa.
 5. The process as recited in claim 1 wherein saidfirst working fluid has a GWPs of less than about
 35. 6. The process asrecited in claim 1, wherein said process that produces heat is at leastone operation associated with at least one industry selected from thegroup consisting of: oil refineries, petrochemical plants, oil and gaspipelines, chemical industry, commercial buildings, hotels, shoppingmalls, supermarkets, bakeries, food processing industries, restaurants,paint curing ovens, furniture making, plastics molders, cement kilns,lumber kilns, calcining operations, steel industry, glass industry,foundries, smelting, air-conditioning, refrigeration, and centralheating.
 7. The process as recited in claim 1, further comprising asecondary heat exchanger loop disposed between said heat exchanger instep (a) and said process which produces said heat.
 8. The process asrecited in claim 7, wherein said secondary heat exchanger loop comprisespassing a secondary fluid in communication with both said heat exchangerand said process which produces said heat, thereby transferring saidheat from said process to said secondary fluid which thereaftertransfers said heat from said secondary fluid to said first workingfluid in liquid phase.
 9. (canceled)
 10. (canceled)
 11. A process forrecovering heat from a heat source and generating mechanical energy,comprising the steps of: (a) compressing a first working fluid in liquidphase above said first working fluid's critical pressure; (b) passingsaid first working fluid from Step (a) through a heat exchanger or afluid heater and heating said first working fluid to a temperature thatis higher or lower than the critical temperature of said first workingfluid, wherein said heat exchanger or said fluid heater is incommunication with said heat source that supplies said heat; (c)removing at least a portion of the heated said first working fluid fromsaid heat exchanger fluid heater; (d) passing said at least a portion ofthe heated said first working fluid to an expander, wherein at leastportion of said heat is converted into mechanical energy, and whereinthe pressure on said first at least a portion of the heated said firstworking fluid is reduced to below the critical pressure of said firstworking fluid, thereby rendering said at least a portion of the heatedsaid first working fluid to a first working fluid vapor or a firstworking fluid mixture of vapor and liquid; (e) passing said firstworking fluid vapor or said first working fluid mixture of vapor andliquid from said expander to a condenser, wherein said at least aportion of said working fluid vapor or said working fluid mixture ofvapor and liquid is fully condensed to a second working fluid in liquidphase; (f) optionally, compressing and mixing said second working fluidin liquid phase with said first working fluid in liquid phase in Step(a); (g) optionally, repeating Steps (a) through (f), at least one time;wherein at least about 20 weight percent of said first working fluidcomprises HFO-1336mzz-Z, HFO-1336mzz-E, or mixtures thereof.
 12. Theprocess as recited in claim 11, wherein the efficiency of convertingheat to mechanical energy (cycle efficiency) is at least about 7%. 13.The process as recited in claim 11, wherein the temperature to which thefirst working fluid is heated in Step (b) is in the range of from about50° C. to about 400° C.
 14. The process as recited in claim 11, whereinthe pressure to which the first working fluid is pressurized in Step (a)is in the range of from about 3 MPa to about 10 MPa.
 15. (canceled) 16.The process as recited in claim 11, wherein said process that producesheat is at least one operation associated with at least one industryselected from the group consisting of: oil refineries, petrochemicalplants, oil and gas pipelines, chemical industry, commercial buildings,hotels, shopping malls, supermarkets, bakeries, food processingindustries, restaurants, paint curing ovens, furniture making, plasticsmolders, cement kilns, lumber kilns, calcining operations, steelindustry, glass industry, foundries, smelting, air-conditioning,refrigeration, and central heating.
 17. The process as recited in claim11, further comprising a secondary heat exchanger loop disposed betweensaid heat exchanger in step (a) and said process which produces saidheat.
 18. The process as recited in claim 13, wherein said secondaryheat exchanger loop comprises passing a secondary fluid in communicationwith both said heat exchanger and said process which produces said heat,thereby transferring said heat from said process to said secondary fluidwhich thereafter transfers said heat from said secondary fluid to saidfirst working fluid in liquid phase.
 19. (canceled)
 20. (canceled)
 21. Acomposition comprising HFO-1336mzz-Z at a temperature in the range offrom about 250° C. to about 300° C., wherein said HFO-1336mzz-Z contentis in the range of from about 50 weight percent to about 99.5 weightpercent.
 22. An Organic Rankine Cycle System extracting heat at anoperating pressure in the range from about 3 MPa to about 10 MPa,wherein said system contains a working fluid, and wherein about 50weight percent of said working fluid comprises HFO-1336mzz-Z,HFO-1336mzz-E, or mixtures thereof.
 23. A composition as working fluidfor power cycles, wherein the temperature of said composition is in therange of from about 200° C. to about 400° C., and wherein about 50weight percent of said composition comprises HFO-1336mzz-Z,HFO-1336mzz-E, or mixtures thereof.
 24. A method for replacing HFC-245fain a power cycle system comprising removing said HFC-245fa from saidpower cycle system and charging said system with a working fluidcomprising at least about 20 weight percent of HFO-1336mzz-Z,HFO-1336mzz-E, or mixtures thereof.
 25. The method of claim 24, whereinthe working fluid comprises a mixture of HFO-1336mzz-Z andHFO-1336mzz-E, and the working fluid comprises at least about 10 weightpercent HFO-1336mzz-E and 90 or more weight percent HFO-1336mzz-Z.